1. Field of the Invention
The present invention relates to an offline power converter, more specifically, the present invention relates to a control circuit of the offline power converter.
2. Description of the Related Art
In conventional offline power converters, a bridge rectifier is utilized to rectify an AC (alternating current) input voltage into a pulsating DC (direct current) input voltage. An input capacitor, such as an electrolytic bulk capacitor, is usually applied at an output of the bridge rectifier to filter the pulsating DC input voltage as a smoother input voltage with small ripple. This bulk capacitor is utilized to store the energy and provide a minimum input voltage to guarantee a proper operation of the offline power converter. However, without the filtering operation of the bulk capacitor, the pulsating direct current input voltage will result in higher output line ripple and none-linearly power converting operation compared to the convention arts. Furthermore, the bulk capacitor generally occupies significant space of the power converter. Whenever the bulk capacitor can be eliminated, the advantages to the power converter will be longer life, smaller size, and greatly reduced manufacturing cost. Therefore, a control circuit capable of regulating an output of the power converter without the need of the bulk capacitor connected to its input is desired by the industries.